Tags: Planet.
Tethys or Saturn III is a mid-sized moon of Saturn about 1060 km (660 mi) across. It was discovered by G. D. Cassini in 1684 and is named after the titan Tethys of Greek mythology. Tethys has a low density of 0.98 g/cm³ indicating that it is made of water ice with just a small fraction of rock. This is confirmed by the spectroscopy of its surface which identified water ice as the dominant surface material. A small amount of an unidentified dark material is present as well.
